Roof bows are attached to vehicle roof structures to strengthen the roof assembly and support the roof rails and roof panel. Roof support pillars are typically located between the windows and doors of a vehicle. Roof support pillars are frequently identified as A, B, C and in some instances D-Pillars depending on the vehicle style. A B-Pillar is generally located immediately behind the front door of a vehicle and is traditionally used to mount the rear door hinges and associated rear doors. The B-Pillar often plays an important role in determining roof strength and the degree of side impact intrusion.
Passenger vehicle designs are tested for roof strength and side impact strength. Improving side impact strength is often addressed by increasing the section size and the thickness of the structural components of the roof rail. Increasing the section size and thickness of the roof rails adds weight to the vehicle, often adds manufacturing costs, and may reduce visibility below the roof rail.